SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42b919492256e6812e2dbc7c14bf7094b579af0122ae79d0717793b03c759423' 
  AND token = 'mzgRnBr4aMIFDCdthPGEBKR7E53lnre7PCInWQEkROc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}